How in-office and ambulatory BP monitoring compare: A systematic review and meta-analysis

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Original Research

How in-office and ambulatory BP monitoring compare: A systematic review and meta-analysis

J Fam Pract. 2017 January;66(1):E5-E12

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References

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METHODS

Most published studies comparing conventional office BP measurement with ABPM have been conducted with patients not taking antihypertensive medication. We excluded these studies and conducted a literature search for studies published up to December 2013 that included hypertensive patients receiving treatment in a primary care setting.

We searched Medline (from 1950 onward) and the Cochrane Database of Systematic Reviews. For the Medline search, we combined keywords for office BP, hypertension, and ambulatory BP with keywords for outpatient setting and primary care, using the following syntax: (((“clinic blood pressure” OR “office blood pressure” OR “casual blood pressure”))) AND (“hypertension” AND ((((“24-h ambulatory blood pressure”) OR “24 h ambulatory blood pressure”) OR “24 hour ambulatory blood pressure”) OR “blood pressure monitoring, ambulatory”[Mesh]) AND ((((((“outpatient setting”) OR “primary care”) OR “family care”) OR “family physician”) OR “family practice”) OR “general practice”)). We chose studies published in English and reviewed the titles and abstracts of identified articles.

With the aim of identifying additional candidate studies, we reviewed the reference lists of eligible primary studies, narrative reviews, and systematic reviews. The studies were generally of good quality and used appropriate statistical methods. Only primary studies qualified for meta-analysis.

Inclusion and exclusion criteria

Acceptable studies had to be conducted in a primary care setting with patients being treated for hypertension, and had to provide data comparing office BP measurement with ABPM. We excluded studies in which participants were treated in the hospital, were untreated, or had not been diagnosed with hypertension.

The quality of the studies included in the meta-analysis was judged by 2 independent observers according to the following criteria: the clear classification and initial comparison of both measurements; explicit and defined diagnostic criteria; compliance with the inclusion/exclusion criteria; and clear and precise definition of outcome variables.

Data extraction

We extracted the following data from each included study: study population, number of patients included, age, gender distribution, number of measurements (ambulatory and office BP), equipment validation, mean office and ambulatory BP, and the period of ambulatory BP measurement. We included adult patients of all ages, and we compared the mean office BP with those obtained by ABPM in hypertensive patients.

STATISTICAL ANALYSIS

For each study, we summarized the diagnostic accuracy of office BP with respect to ABPM in terms of sensitivity, specificity, and positive and negative likelihood ratios (LRs), with the 95% confidence interval (CI), if available. If these rates were not directly reported in the original papers, we used the published data to calculate them.

The likelihood of under- or overestimating BP control is high when relying on in-office measurement alone.

We used the R v2.15.1 software with the “mada” package for meta-analysis.¹⁴ Although a bivariate approach is preferred for the meta-analysis of diagnostic accuracy, it cannot be recommended if the number of primary studies to pool is too small,¹⁴ as happened in our case. Therefore, we used a univariate approach and pooled summary statistics for positive LR, negative LR, and the diagnostic odds ratio (DOR) with their 95% confidence intervals. We used the DerSimonian-Laird method to perform a random-effect meta-analysis. To explore heterogeneity between the studies, we used the Cochran’s Q heterogeneity test, I² index, and Galbraith and L’Abbé plots.

RESULTS

Our search identified 237 studies, only 12 of which met the inclusion criteria and contained data to calculate the differences between the means of office and ambulatory BP measurements (TABLES 1 AND 2).^15-26 Of these 12 studies, 5 were suitable for calculating sensitivity, specificity, and LR (TABLE 3),^{16,18,22,24,26} and 4 contained sufficient extractable data for meta-analysis. The study by Little et al¹⁸was not included in the meta-analysis, as the number of true-positive, true-negative, false-positive, and false-negative results could not be deduced from published data.

The studies differed in sample size (40-31,530), patient ages (mean, 55-72.8 years), sex (percentage of men, 31%-52.9%), and number of measurements for office BP (1-9) and ABPM (32-96) (TABLE 1),^15-26 as well as in daytime and nighttime periods for ABPM and BP thresholds, and in differences between the mean office and ambulatory BPs (TABLE 2).^15-26

In general, the mean office BP measurements were higher than those obtained with ABPM in any period—from 5/0 mm Hg to 27.4/10.1 mm Hg in the day, and from 7.9/6.3 mm Hg to 31.2/13.7 mm Hg over 24 hours (TABLE 2).^15-26

Compared with ABPM in diagnosing uncontrolled BP, office BP measurement had a sensitivity of 55.7% to 91.2% and a specificity of 25.8% to 61.8% (depending on whether the measure was carried out by the doctor or nurse¹⁸); positive LR ranged from 1.2 to 1.4, and negative LR from 0.3 to 0.72 (TABLE 3).^{16,18,22,24,26}

For meta-analysis, we pooled studies with the same thresholds (140/90 mm Hg for office BP; 130/80 mm Hg for ABPM), with diagnostic accuracy of office BP expressed as pooled positive and negative LR, and as pooled DOR. The meta-analysis revealed that the pooled positive LR was 1.35 (95% CI, 1.32-1.38), and the pooled negative LR was 0.44 (95% CI, 0.37-0.53). The pooled DOR was 3.47 (95% CI, 3.02-3.98). Sensitivity was 81.9% (95% CI, 74.8%-87%) and specificity was 41.1% (95% CI, 35.1%-48.4%).

One study¹⁶ had a slightly different ambulatory diagnostic threshold (133/78 mm Hg), so we excluded it from a second meta-analysis. Results after the exclusion did not change significantly: positive LR was 1.39 (95% CI, 1.34-1.45); negative LR was 0.38 (95% CI, 0.33-0.44); and DOR was 3.77 (95% CI, 3.31-4.43).

In conclusion, the use of office-based BP readings in the outpatient clinic does not correlate well with ABPM. Therefore, caution must be used when making management decisions based solely on in-office readings of BP.